This invention relates to electrical components and methods for their fabrication. More particularly, the invention relates to highly reliable electrical components in which cured silicone coated on an electrical element has been thoroughly monolithically adhered with cured resin sealant coated on the cured silicone. The invention also relates to a highly productive method for fabricating the electrical components.
Electrical elements, e.g., integrated circuits, hybrid integrated circuits, semiconductor chips, transistors, diodes, capacitors, resistors, etc., are generally coated with a cured resin sealant. The sealant protects the element from external stresses (flexural stresses, impact, etc.), prevents water infiltration, and improve moistures resistance. In addition, the electrical element may also be coated with cured silicone to protect it from internal stresses originating from the expansion and shrinkage of the cured resin sealant. However, the cured silicone does not bond or adhere to the over-coated cured resin sealant, which results in unacceptable reliability for the resin-sealed electrical component.
To date, monolithic bonding between the cured silicone coating the electrical element and the cured sealant resin over-coating the cured silicone has been pursued by treating the surface of the cured silicone with ultraviolet radiation and sealing this UV-treated cured silicone with the resin sealant (U.S. Pat. No. 4,645,551, JP-A-64-27249, JP-A-1-94679, JP-A-2-27756, and JP-A-3-22553).
However, even electrical components of this type suffer from an unacceptable adherence between the cured silicone and the cured resin sealant. As a result, the reliability of these resin-sealed electrical components remains unsatisfactory. Moreover, the methods for fabricating these electrical components suffer from poor productivity because they require irradiation with ultraviolet light.
Therefore, an object of the present invention is to provide highly reliable electrical components with the cured silicone coating the electrical element thoroughly bonded into a monolithic mass with the cured resin sealant coated on the cured silicone. A further object of this invention is to provide a highly productive method for the fabrication of the electrical components.